1. Technical Field
The present invention relates to an electrophoresis display device and an electronic apparatus.
2. Related Art
An electrophoresis display device is known in the technical field to which the present invention pertains. An electrophoresis display device that is known in the art displays an image by utilizing an electrophoresis phenomenon. Electrophoresis is a phenomenon that can be roughly defined as the migration of electrically charged particles that are dispersed in liquid, which occurs as a result of application of a voltage thereto. An example of an electrophoresis display device of the related art is described in JP-A-2005-148711. In a popular configuration of an electrophoresis display device of the related art, an electrophoresis material layer is sandwiched between a pair of substrates that are provided opposite to each other. In the electrophoresis material layer that is interposed between these substrates that face each other, electrically charged minute particles are dispersed in a solvent. Recently, an active-matrix electrophoresis display device has become one of the leading mainstreams among a variety of the related-art electrophoresis display devices.
In a typical configuration of an active-matrix electrophoresis display device of the related art, a common electrode is formed on the inner surface of one of the above-mentioned pair of substrates, or more specifically, one substrate that is provided at a display side thereof. On the other hand, pixel electrodes, switching elements, wirings, and the like, are formed on another substrate that is provided at a non-display side opposite to the display side of the above-mentioned one substrate. Generally speaking, the “numerical aperture”, that is, opening ratio, of a substrate is relatively low if switching elements, wirings, and the like, are formed thereon. In order to prevent the opening ratio of the display-side substrate, which is closer to a viewer and thus should have a high opening ratio, from being decreased, these switching elements, wirings, and the like, are not formed on the viewer-side substrate but formed on the other substrate that is provided opposite to the viewer-side substrate.
The related-art electrophoresis display device having such a typical configuration operates as follows. For example, if it is assumed that electrically charged particles thereof are charged negative (i.e., electronegative), the electrically charged particles move in a direction that is reverse to an electrostatic direction, or in other words, in a direction that is reverse to an electric-field direction, upon the generation of an electric field between a pixel electrode and a common electrode. When the electrically charged particles move to the surface of the common electrode, the coloration of the electrically charged particles is visually recognized at the display side. On the other hand, when the electrically charged particles move to the surface of the pixel electrode, the coloration of the solvent is visually recognized at the display side.
In a typical configuration of an electrophoresis display device known in the art, the above-explained electrophoresis configuration is formed for each of a plurality of pixels. The migration, that is, movement, of the electrically charged particles of electronic ink is controlled on a pixel-by-pixel basis. By this means, the related-art electrophoresis display device is capable of displaying a variety of images such as a still picture and a moving picture. In another recent configuration of an electrophoresis display device known in the art, electronic ink is filled inside a microcapsule.
As an advantageous aspect of the electrophoresis display device of the related art, it is capable of retaining a display state for a certain length of a time period. Having such a unique characteristic, it is expected that the electrophoresis display device of the related art can be used as a variety of devices that employs electronic paper. One non-limiting application example of the electrophoresis display device of the related art in the technical field of electronic paper is an electronic personal organizer. In the application of an electrophoresis display device to an electronic personal organizer, in order to improve user-friendliness thereof, it is preferable that the device should be provided not only with an image display function but also with a handwritten input function. As one related-art technique for offering a handwritten input capability, an active-matrix electrophoresis display device of the related art is provided with optical sensors such as photodiodes or the like that are formed on an array substrate on which pixels electrodes, switching elements, and the like are formed. An example of the active-matrix electrophoresis display device of the related art having such an optical sensing configuration is described in JP-A-11-75115.
Disadvantageously, however, since an electrophoresis display device is configured in such a manner that electrically charged particles or a dispersion medium is observed, incident light that enters through the display-side substrate is shut off by the electrically charged particles and/or the dispersion medium; as a result thereof, little light reaches the array substrate. If optical sensors are arrayed on an array substrate that is provided at a non-display side without any technical structure that facilitates optical transmission thereof, it is hard for incident light that enters through the display-side substrate to reach the optical sensors formed on the non-display-side substrate. This makes it difficult to increase the application range of an electrophoresis display device.